Horsetail
Scientific Name(s): Equisetum arvense L., Equisetum myriochaetum
Common Name(s): Bottle brush, Dutch rushes, Horse willow, Mexican giant horsetail, Paddock-pipes, Pewterwort, Scouring rush, Shave grass, Toadpipe
Medically reviewed by Drugs.com. Last updated on Nov 22, 2022.
Clinical Overview
Use
Horsetail has traditionally been used as a diuretic, an astringent to stop bleeding and stimulate the healing of wounds and burns, and as a cosmetic component. In addition, it has been used for the treatment of tuberculosis and for kidney and bladder ailments (eg, urethritis, cystitis with hematuria); however, clinical trials are lacking to support these uses. Clinical data demonstrates a hypoglycemic effect with the use of E. myriochaetum and efficacy in treating brittle nails with use of E. arvense.
Dosing
Equisetum palustre products are contraindicated for use in humans. Brittle nails: A formulation containing E. arvense applied topically every night for 28 days or every other day for 14 days has been used to strengthen fingernails in clinical trials. Diuretic: A dry extract of the aerial parts of E. arvense containing 0.026% total flavonoids has been administered as 300 mg orally 3 times daily. Type 2 diabetes: A water extract of a related species of horsetail (E. myriochaetum) as a single oral dose of 0.33 g/kg has been used in a clinical study. Wound healing: An E. arvense 3% ointment applied topically every 12 hours for 10 days has been used following episiotomy in postpartum mothers.
Contraindications
Horsetail has been listed as an herb of undefined safety by the US Food and Drug Administration (FDA). Horsetail remedies prepared from E. arvense are generally considered safe when used properly. However, another species of horsetail, E. palustre, is poisonous to horses and contraindicated for use in humans.
Pregnancy/Lactation
Avoid use. Information regarding safety and efficacy in pregnancy and lactation is lacking.
Interactions
The therapeutic effect of efavirenz may be diminished by horsetail.
Adverse Reactions
Documented adverse effects possibly associated with horsetail include acute pancreatitis and an isolated incident of headache.
Toxicology
Horsetail has been listed as an herb of undefined safety by the FDA. Horsetail remedies prepared from E. arvense are generally considered safe when used properly. However, another species of horsetail, E. palustre, is poisonous to horses and contraindicated for use in humans. E. arvense may be toxic, especially in cases of underlying liver disease. There have been reports of children being poisoned by using the stems as blowguns or whistles.
Related/similar drugs
Ginkgo Biloba, turmeric, milk thistle
Scientific Family
- Equisetaceae
Botany
E. arvense is native to Europe, North America, North Africa, and Northern AsiaChevalier 1996 and grows best in moist and shady areas.Weiss 1992 Horsetail is a pteridophyte more closely related to ferns than to flowering plants; it produces spore sacs that are visible from March through September.Hallowell 1994 The plant is a small, deep-rooted, rush-like perennial that grows about 0.3 m in height. It has hollow, pointed stems, scale-like leaves, and no flowers. Mexican giant horsetail (E. myriochaetum) is a species of horsetail native to regions of South America.Revilla 2002
History
The word "Equisetum" is derived from the Latin "equus," meaning "horse," and "seta," meaning "bristle."(UMMC 2017) The plant has traditionally been used as a diuretic, and in the treatment of tuberculosis,(Gruenwald 2000) genitourinary and respiratory disorders, arthritis, and bleeding ulcers.(Lininger 1998) Because of its abrasive texture (due to its high silica content), horsetail has been used to clean dishes, sand wood, and polish metal.(Weiss 1992) Externally, horsetail has been used in cosmetics(Boruch 1984) and as an astringent to stop bleeding(Schauenberg 1977) and stimulate wound healing (due to its free silica content).(Asgharikhatooni 2015, Duke 1985, Gruenwald 2000) E. myriochatum has been used in traditional medicine to treat kidney disease and type 2 diabetes.(Revilla 2002)
Chemistry
The stems of horsetail contain 5% to 8% silica and silicic acids. The plant contains about 5% of a saponin called equisetonin, as well as the flavone glycosides isoquercitrin, equisetrin, and galuteolin.(Tyler 1987) The sterol fraction of E. arvense contains beta-sitosterol, campesterol, isofucosterol, and trace amounts of cholesterol.(D'Agostino 1984) The alkaloid nicotine is also present in minute amounts (less than 1 ppm),(Tyler 1987) but may account for a portion of the pharmacological activity of the plant. The plant contains more than 15 types of bioflavonoids, as well as manganese, potassium, sulfur, and magnesium.(Bisset 2001, Lininger 1998) The cytokinin isopentenyladenosine has been identified in fertile fronds.(Yamane 1983)
Uses and Pharmacology
Brittle Nails
Clinical data
In 2 clinical trials evaluating a formulation of E. arvense (a plant extract rich in organic silica) and a sulfur donor in a hydroalcoholic solution (hydroxypropyl chitosan [HPCH]), improvements in nail alterations (eg, splitting, fragility, longitudinal grooves) were observed. The organic silica properties of E. arvense serve to harden and strengthen the nail, while HPCH improves nail hydration, and the sulfur donor supports nail growth.(Sparavigna 2006)
Gout
The American College of Rheumatology, for its 2012 guidelines on the management of gout, voted that the use of various oral complementary agents, including horsetail, was inappropriate for the treatment of an acute attack of gout. The new guideline (2020) based on additional evidence regarding the management of gout no longer included a statement regarding the use of horsetail.(Fitzgerald 2020, Khanna 2012)
Neuroprotective effects
In vitro and in vivo data
The neuroprotective activity of 3 Equisetum species ethanolic extracts using zebrafish tests were determined in vivo. The results indicated that E. sylvaticum extract has a significant antioxidant activity; whereas, E. pratense extract had anxiolytic and antidepressant effects significantly higher than the other 2 extracts used. Promising results for the antioxidant in vitro tests as well as the neuroprotective activity of in vivo tests for various ethanolic extracts from Equisetum species were noted.(Batir-Marin 2021)
Osteoporosis
Animal data
In a study of rats, the addition of an ethanolic extract of E. arvense to an anabolic nutrient mixture containing calcium carbonate, vitamin D, zinc sulfate, L-lysine, L-proline, L-arginine, and L-ascorbic acid was beneficial for bone formation; it was also more effective in preventing osteoporotic bone loss compared with raloxifene. Because of its high silica content, E. arvense may increase efficacy of the formulated nutrient mixture used for the treatment of osteoporosis and may aid in the prevention of osteoporosis; however, clinical trials are lacking.(Kotwal 2016)
Pancreatic carcinoma
In vitro data
In vitro testing of Equisetum arvense ethanolic extracts induced cell death in pancreatic carcinoma AsPC-1 cells.(Bhat 2020)
Urological effects
The horsetail plant exerts slight diuretic activity, possibly due to the high concentrations of flavonoids, phenolic compounds, and mineral salts found in the aerial parts of E. arvense. In addition, a review article concluded that Equisetum species have great potential in the management of kidney disorders.(Boeing 2021)
Historical reports of the use of horsetail in the treatment of urological disorders such as cystitis and urinary tract infections exist. Although horsetail shows some promise for the treatment of overactive bladder, there are no clinical data demonstrating this efficacy.(Chughtai 2013)
Clinical data
In a randomized, double-blind trial of 36 healthy male volunteers, diuretic effects comparable with those of hydrochlorothiazide 25 mg and superior to placebo were observed with E. arvense 900 mg/day. No changes in electrolytes or liver, kidney, or hematological function tests were observed, and adverse reactions were mild and infrequent. E. arvense was deemed safe for oral acute use.(Carneiro 2014)
Wound Healing
Clinical data
In a clinical trial of postpartum mothers, an E. arvense 3% ointment improved wound healing and pain intensity following episiotomy, based on reductions in scores on the Redness, Edema, Ecchymosis, Discharge and Approximation of the Edges (REEDA) scale.(Asgharikhatooni 2015)
In terms of innovative dressing materials, chitosan-based hydrogels that have been modified with E. arvense L. extracts have demonstrated beneficial effects.(Głab 2021)
Dosing
E. palustre products are contraindicated for use in humans.
Brittle nails: A formulation containing E. arvense and a sulfur donor in an HPCH solution applied topically every night for 28 days in one trial, or every other day (preferably in the evening) for 14 days in another trial to strengthen fingernails.(Sparavigna 2006)
Diuretic: A dry extract of the aerial parts of E. arvense containing 0.026% total flavonoids was administered as 300 mg orally 3 times daily for 4 days (total daily dose of 900 mg, the maximum recommended dose for dry extracts) in a clinical trial of healthy volunteers.(Carneiro 2014)
Type 2 diabetes: A water extract of another species of horsetail (E. myriochaetum) as a single oral dose of 0.33 g/kg was used in a clinical study evaluating the hypoglycemic effects of horsetail.(Revilla 2002)
Wound healing: An E. arvense 3% ointment applied topically every 12 hours for 10 days was used following episiotomy in postpartum mothers.(Asgharikhatooni 2015)
Pregnancy / Lactation
Avoid use. Information regarding safety and efficacy in pregnancy and lactation is lacking.Revilla 2002
Interactions
Efavirenz: Horsetail may diminish the therapeutic effect of efavirenz. Monitor therapy.(Cordova 2017)
Adverse Reactions
Research reveals limited information regarding adverse reactions with the use of horsetail; however, there was an isolated report of strong headache in 1 clinical trial from the use of a dry extract from the aerial parts of E. arvense.(Carneiro 2014) In another isolated report, a possible link between habitual consumption of horsetail infusions and recurrent episodes of acute pancreatitis were documented after all other etiologies were ruled out.(García-Gavilán 2017) A case of hyponatremia attributed to decreased oral intake and syndrome of inappropriate secretion of antidiuretic hormone (due to nausea) possibly exacerbated by the diuretic effect of horsetail (E. arvense) has been reported.(Bates 2021)
Individuals allergic to nicotine should avoid horsetail because of its nicotine content; one case of dermatitis has been reported.(Sudan 1985)
Toxicology
Horsetail has been listed as an herb of undefined safety by the FDA.(Fetrow 2000) Horsetail remedies prepared from E. arvense are generally considered safe when used properly. However, another species of horsetail, such as E. palustre, is poisonous to horses and contraindicated for use in humans.(UMMC 2017) Few in vivo toxicity studies have been conducted for most Equisetum species, so there is no consensus on an effective non-toxic dosage.(Boeing 2021)
Ingestion of large amounts of E. arvense fern may be toxic. There have been reports of children being poisoned by using the stems as blowguns or whistles.(Leung 1996) Crude horsetail contains the enzyme thiaminase, which destroys the B vitamin thiamine. Thiaminase poisoning may lead to permanent liver damage; preclinical studies have revealed various pharmacological actions of E. arvense, but no acute hepatotoxicity.(Carneiro 2014, Hallowell 1994) The Canadian Health Protection Branch prohibits thiaminase in dietary supplements, and supplement manufacturers must provide supportive documentation of its removal.(Lininger 1998) In a case report, a 52-year-old man who had consumed horsetail juice (500 mL/day for 2 weeks) and who had osteoarthritis, renal colic, and asymptomatic underlying chronic liver disease secondary to hepatitis B infection developed acute hepatitis; symptoms developed after consuming the juice for 1 week.(Klncalp 2012) In a clinical trial of healthy volunteers, oral use of E. arvense at 900 mg daily (in 3 divided doses) produced no signs of liver, kidney, hematological, or electrolyte toxicity.(Carneiro 2014)
In animals, ingestion of horsetail produces muscle weakness, ataxia, weight loss, abnormal pulse rate, cold extremities, and fever,(Klncalp 2012) symptoms similar to those occurring with nicotine intoxication. Hay composed of 20% or more of E. arvense produced these symptoms in 2 to 5 weeks.(Duke 1985) E. arvense may also induce seborrheic dermatitis in animals.(Kamphues 1990, Sudan 1985)
E. palustre contains toxic alkaloids(Bisset 2001, Lininger 1998). Cattle appear to recognize the odor of this species of horsetail and refuse to eat hay contaminated with E. palustre at a concentration of about 12%.(Spoerke 1980)
Index Terms
- Equisetum palustre
References
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